Update site definitions

[emstoudenmire]

• Update keyword args style of Electron space function and test
• Update keyword args of Fermion space function and test
• Update Fermion op function overloads to use op!
• Update Electron op overloads to use op!
• Update generic "Id" op overload to use op!
• Update keyword argument style for tJ space function
• Update tJ op overloads to use op! and fix Sx defn

[mtfishman]

Great, thanks for tackling this!